This invention relates to touch sensitive holographic image display systems, in particular to systems which are able to project onto a surface at an acute angle. The invention also provides related methods and corresponding processor control code.
We have previously described techniques for displaying an image holographically—see, for example, WO 2005/059660 (Noise Suppression Using One Step Phase Retrieval), WO 2006/134398 (Hardware for OSPR), WO 2007/031797 (Adaptive Noise Cancellation Techniques), WO 2007/110668 (Lens Encoding), and WO 2007/141567 (Colour Image Display). These are all hereby incorporated by reference in their entirety.
Projecting downwards and outwards onto a flat surface such as a tabletop entails projecting at an acute angle onto the display surface (taking this as the angle between the centre of the output of the projection optics and the middle of the displayed image—this angle, to a line in the surface, is less that 90°). We conveniently refer to this as “table down projection”. Table down projection is not readily achievable by conventional image display techniques; scanning image display systems have a narrow throw angle and thus find it difficult to achieve a useful image size whilst projection systems, especially those based on LEDs (light emitting diodes)
which have a wide light output angle, find it difficult to achieve a useful depth of field. Moreover table down projection can often involve very substantial distortion of an image which can result in inefficient use of the area of an image display device, resulting in major reductions in image brightness and overall system efficiency. Background information relating to compensating for keystone distortion in an LCD projector can be found in U.S. Pat. No. 6,367,933 (WO00/21282); further background prior art can be found in: WO02/101443; U.S. Pat. No. 6,491,400; U.S. Pat. No. 7,379,619; US2004/0095315; U.S. Pat. No. 6,281,878; and U.S. Pat. No. 6,031,519.
The inventors have recognized that holographic image display techniques can be used to address these problems to provide a wide throw angle, long depth of field, and very substantial distortion correction without substantial loss of brightness/efficiency. These techniques are described in our UK Patent Application number GB0822336.4 filed on 8 Dec. 2008 hereby incorporated by reference in its entirety.
Background prior art relating to touchsensing can be found, for example, in patent applications filed by Lumio Inc (such as WO2008/038275) and VKB Inc (such as US2007/222760), as well as in patent/applications filed by Canesta Inc (for example U.S. Pat. No. 6,323,942), and patent applications filed by Sensitive Object (such as WO2006/108443 and WO2008/146098).
Hence, for at least the aforementioned reasons, there exists a need in the art for advanced systems and methods for display.